Two-dimensional material testing device of terahertz time-domain spectroscopy and parameter extraction method thereof

Abstract

The present application relates to the field of terahertz time-domain spectroscopy, and discloses a two-dimensional material testing device for terahertz time-domain spectroscopy and a parameter extraction method thereof.The device comprises a beam splitter for transmitting light rays of a light source to form first split light rays and for reflecting light rays of the light source to form second split light rays;a plurality of metal mirrors for reflecting and adjusting light paths;a half-wave plate for ensuring that the first split light rays form linearly polarized light rays;a LiNbO3 crystal sheet for exciting terahertz light rays from the first split linearly polarized light rays;a plurality of parabolic mirrors for reflecting the terahertz light rays to irradiate two-dimensional materials to form THz light rays containing material measurement information;a material substrate for placing the two-dimensional materials;a silicon wafer for reflecting the second split light rays and transmitting the THz light rays containing the material measurement information to make them collinear to form analysis incident light rays;a spectrum analyzer for electrically sampling and calculating the analysis incident light rays, and for generating a testing result of the two-dimensional materials according to an extraction parameter formula.

Description

Technical Field

[0001] This invention relates to the field of terahertz time-domain spectroscopy measurement, and more particularly to a two-dimensional material testing device for terahertz time-domain spectroscopy and a method for extracting its parameters. Background Technology

[0002] Transmission terahertz time-domain spectroscopy and reflection terahertz time-domain spectroscopy have become powerful tools for studying carrier dynamics in liquids, bulk materials, thin films, and two-dimensional materials. They can extract the complex photoconductivity, complex permittivity, and complex refractive index of materials from the spectra, enabling the analysis of the unique physical mechanisms of particles (e.g., free carriers, excitons, and dipoles) in the terahertz range. Due to their unique electronic and optical properties, two-dimensional materials are considered key components for next-generation optoelectronic, photovoltaic, and nanoelectronic devices. In recent years, terahertz time-domain spectroscopy measurements have been widely applied to study carrier dynamics in two-dimensional materials. Therefore, establishing comprehensive methods for extracting the optical parameters of two-dimensional materials has become an urgent need for terahertz time-domain spectroscopy measurement techniques.

[0003] Typically, the thickness of two-dimensional materials ranges from a few nanometers to tens of nanometers, making them difficult to self-support and requiring a substrate, i.e., a two-dimensional material / substrate system. Researchers often employ thin-film parameter extraction methods based on the thin-film / substrate system to extract the optical parameters of two-dimensional materials. Several commonly used parameter extraction methods have been proposed to date. For example, there are Tinkham's formula for transmission terahertz time-domain spectroscopy and optical parameter extraction methods for reflection terahertz time-domain spectroscopy, such as the method used by F. Gao et al. in 1996 to study vertically incident YBa₂Cu₃O₃ in the far-infrared band. 7-δ For thin films, a concise method for extracting transmission and reflection spectral parameters considering surface currents has been proposed. These methods can accurately and rapidly extract sample parameters under certain conditions. However, for terahertz time-domain spectroscopy, which can simultaneously measure spectral amplitude and phase, these methods obviously have significant drawbacks, such as neglecting phase difference, angle, and polarization factors. Therefore, it is necessary to further extend the methods for accurately extracting the optical parameters of two-dimensional materials in the terahertz band. Summary of the Invention

[0004] The main objective of this invention is to solve the technical problem that current terahertz time-domain spectroscopy methods for measuring spectral amplitude and phase are not accurate enough and ignore factors such as phase difference, angle, and polarization.

[0005] The first aspect of this invention provides a two-dimensional material testing device for terahertz time-domain spectroscopy, the device comprising:

[0006] A beam splitter is used to transmit light from a light source to form a first beam split, and to reflect light from a light source to form a second beam split;

[0007] Multiple metal mirrors are used to reflect and adjust the light from the source, forming a reflective terahertz time-domain optical path and a transmissive terahertz time-domain optical path.

[0008] A half-wave plate is used to ensure that the first beam splitter is a linearly polarized beam.

[0009] LiNbO3 crystal sheet is used to diffract the linearly polarized light to form terahertz excitation light;

[0010] Multiple parabolic mirrors are used to reflect the terahertz excitation light to irradiate the two-dimensional material and form THz light containing material measurement information;

[0011] A material substrate for placing two-dimensional materials and for adjusting the incident angle of the terahertz excitation light irradiating the two-dimensional materials;

[0012] A silicon wafer is used to reflect the second beam splitter and transmit the THz light containing material measurement information in a collinear manner to form the analytical incident light;

[0013] A spectral analyzer is used for electro-optic sampling and calculation of the incident light to generate test results for two-dimensional materials.

[0014] Optionally, in a first implementation of the first aspect of the present invention, the material substrate includes a sapphire substrate.

[0015] Optionally, in a second implementation of the first aspect of the present invention, the sapphire substrate comprises a sapphire sheet with a thickness of 260 μm.

[0016] Optionally, in a third implementation of the first aspect of the present invention, the placement of the two-dimensional material includes: aggregating the two-dimensional material on a copper foil based on CVD technology, and placing the two-dimensional material on the copper foil on the material substrate.

[0017] Optionally, in a fourth implementation of the first aspect of the present invention, the spectral analyzer includes a ZnTe crystal sheet for photoelectric acquisition of the incident light for analysis.

[0018] Optionally, in a fifth implementation of the first aspect of the present invention, the metal reflector includes: an Au reflector and an Ag reflector.

[0019] Optionally, in a sixth implementation of the first aspect of the present invention, the two-dimensional material testing device for terahertz time-domain spectroscopy further includes a convex lens, which is disposed in the propagation path of the second beam of light between the plurality of metal mirrors and the silicon wafer, for focusing the second beam of light into the silicon wafer.

[0020] A second aspect of the present invention provides a method for extracting two-dimensional material parameters from terahertz time-domain spectra, the method comprising:

[0021] The light from the generated light source enters the beam splitter to obtain the first and second beam splits;

[0022] The second beam of light is adjusted by using the reflection of multiple metal mirrors so that the second beam of light enters the silicon wafer;

[0023] The reflection of the first beam of light is adjusted by using multiple metal mirrors so that the first beam of light enters the half-wave plate, ensuring that the linearly polarized light is diffracted by the LiNbO3 crystal plate to generate terahertz excitation light.

[0024] By using multiple parabolic mirrors to reflect and adjust the terahertz excitation light, the terahertz excitation light is incident on the two-dimensional material on the material substrate to generate THz light containing material measurement information;

[0025] Multiple parabolic mirrors are used to reflect and adjust the THz light for material measurement information, so that the material measurement light enters the silicon wafer;

[0026] The silicon wafer is used to receive the second beam of light and the THz light containing material measurement information to form the analytical incident light, and the analytical incident light is controlled to enter the spectrometer.

[0027] The spectral analyzer generates the photoconductivity of two-dimensional materials based on a preset signal acquisition algorithm.

[0028] Optionally, in a first implementation of the second aspect of the present invention, the spectral analyzer generates the photoconductivity of the two-dimensional material based on a preset signal acquisition algorithm, including:

[0029] Substituting the reflection measurement data into the signal analysis formula yields the photoconductivity of the two-dimensional material, wherein the signal analysis formula includes:

[0030]

[0031]

[0032]

[0033]

[0034] Substituting the transmission measurement data into the signal analysis formula yields the photoconductivity of the two-dimensional material, wherein the signal analysis formula includes:

[0035]

[0036]

[0037]

[0038]

[0039] When using a flat dielectric or metal surface as a reference It is the transmission reference electric field. The electric field measured is the sample electric field, ΔΨ is the measured phase difference, and t(ω) is the measured amplitude ratio. To measure the value of the complex reflection function, The substrate transmittance is , Let E be the sample transmittance coefficient, where E is the transmittance coefficient. THz (ω) is the electric field of the incident terahertz wave. It is a reflected reference electric field. The electric field measured on the sample, ω is the angular frequency. Here, ΔΦ is the air transfer factor, ΔΦ is the measurement phase difference, and r(ω) is the measurement amplitude ratio. To measure the value of the complex reflection function, The substrate reflectance is... Let θ be the sample reflectance coefficient. in Let n be the incident angle, n1 be the air refractive index, n2 be the substrate refractive index, and Z0 be the free-space impedance. The p-polarized complex optical conductivity of the sample. The polarization complex optical conductivity of the sample is S.

[0040] Optionally, in a second implementation of the second aspect of the present invention, the signal analysis formula further includes:

[0041]

[0042] in, The photoconductivity of the sample is [value missing]. The p-polarized complex optical conductivity of the sample. The polarization complex optical conductivity of the sample is S.

[0043] In this embodiment, the accuracy and versatility of the method are determined through experimental measurements and parameter extraction of the sample. The obtained results can be used to accurately extract the optical parameters of two-dimensional material / substrate systems, which is of great significance for accurately evaluating the physical properties of materials and various applications of terahertz time-domain spectroscopy (such as imaging and identification). This significantly promotes the overall improvement of terahertz time-domain spectroscopy measurement technology and advances the exploration of two-dimensional materials in the terahertz band. This not only greatly simplifies user operation but also improves the consistency of measurement indicators, enhancing practicality and reliability. It solves the technical problems of current terahertz time-domain spectroscopy methods for measuring spectral amplitude and phase, which are not precise enough and neglect factors such as phase difference, angle, and polarization. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of one embodiment of the two-dimensional material testing device for terahertz time-domain spectroscopy in this invention.

[0045] Figure 2a A schematic diagram showing the variation of photoconductivity and frequency of the sample;

[0046] Figure 2b A schematic diagram showing the photoconductivity of ML-MoS2 on a sapphire substrate measured by transmission terahertz time-domain spectroscopy and reflection terahertz time-domain spectroscopy.

[0047] Figure 3 This is a schematic diagram of an embodiment of the two-dimensional material testing method using terahertz time-domain spectroscopy in this invention.

[0048] Figure 4 This is a schematic diagram illustrating the principles of transmission and reflection in an embodiment of the present invention. Detailed Implementation

[0049] This invention provides a two-dimensional material testing device and method for terahertz time-domain spectroscopy.

[0050] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” or “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0051] For ease of understanding, the specific process of the embodiments of the present invention is described below. Please refer to [link / reference]. Figure 1 One embodiment of the two-dimensional material testing device for terahertz time-domain spectroscopy in this invention includes:

[0052] A beam splitter (BS) is used to transmit light from a source (fs) to form a first beam splitter and to reflect light from a source to form a second beam splitter; multiple metal mirrors (M1-M13) are used to reflect and adjust the optical paths of the light from the source (fs), the first beam splitter, and the second beam splitter; a half-wave plate (HWP) is used to form linearly polarized light from the first beam splitter; a LiNbO3 crystal sheet is used to diffract the linearly polarized light to form terahertz excitation light; multiple parabolic mirrors (PM1-PM5) are used to reflect the terahertz light to irradiate the two-dimensional material to form material measurement light; a material substrate is used to place the two-dimensional material and to adjust the incident angle of the terahertz light irradiating the two-dimensional material; a silicon wafer (Si) is used to receive the second beam splitter and the material measurement light to form analytical incident light; and a spectrometer is used to receive and calculate the analytical incident light to generate test results for the two-dimensional material.

[0053] Specifically, the system includes a beam splitter for splitting the femtosecond laser beam. The first beam is used to pump a LiNbO3 crystal to generate a terahertz irradiation source, and the second beam, after a time delay, is used for time-domain detection of the transmitted and reflected photoelectric fields. Multiple metal mirrors form the optical path for the femtosecond pump source, the first beam splitter, the second beam splitter, and the transmission and reflection measurements in the terahertz time-domain spectroscopy system. A half-wave plate refracts the first beam splitter to ensure linear polarization. A LiNbO3 crystal sheet forms the terahertz source under the pump of the first beam splitter. Multiple parabolic mirrors focus the terahertz light onto a two-dimensional material for transmission and reflection measurements. A material substrate is used to hold the two-dimensional material. A silicon wafer is used to allow the transmitted or reflected beams of the first and second beam splitters to collinearly incident on the ZnTe detector crystal. A spectrometer is used for electro-optic sampling and detection of the terahertz light transmitted through or reflected from the sample to obtain test results.

[0054] exist Figure 1 In the diagram, part a is the transmission terahertz time-domain spectrum (TDTS), and part b is the reflection terahertz time-domain spectrum (TDRS). The PM in part b is a semi-transparent and semi-reflective mirror.

[0055] In one embodiment, terahertz time-domain spectroscopy measurement is performed in... Figure 1The experiment was conducted using the standard configuration shown, including transmission and reflection modules. A 1kHz Ti:sapphire mode-locked laser amplification system was employed, which generates laser pulses with a wavelength of 800nm, photon energy of 1.5eV, and pulse width of 30s. The incident beam was split into two parts by a beam splitter (BS): one beam was used to generate terahertz radiation, and the other was used for detection.

[0056] The generated beam is focused onto the LiNbO3 crystal using wavefront tilting technology to generate terahertz waves, which are then propagated and focused onto the sample through metal parabolic mirrors (PM1–PM5).

[0057] In one embodiment, the metal reflector includes: an Au reflector and an Ag reflector.

[0058] In one embodiment, the spectral analyzer includes a ZnTe crystal chip for photoelectric acquisition of the incident light beam, detecting collinearity between the beam and the transmitted terahertz pulse, and collecting the light using ZnTe crystal electro-optic sampling, which is then received by the spectral analyzer. A terahertz time-domain signal is obtained by measurement using a lock-in amplifier and a terahertz signal acquisition program written in LabVIEW.

[0059] In one embodiment, the measured two-dimensional material was molybdenum disulfide (MoS2), a novel two-dimensional material with a band gap of 1.29 eV. The band gap widens with decreasing layer number, and when the number of layers is reduced to a single layer, the indirect band gap becomes a direct band gap of approximately 1.90 eV. The feasibility of the extended extraction parameter model was determined using monolayer MoS2. ML-MoS2 nanosheets with an area of ​​1 cm × 1 cm were synthesized on copper foil using standard CVD technology and then transferred to a sapphire substrate. The thickness of the sapphire substrate was d = 260 μm. The refractive index was 3.04 in the 0.1–2 terahertz band. The photoconductivity of ML-MoS2 at different incident angles was verified using transmission terahertz time-domain spectroscopy. Please refer to [reference needed]. Figure 2a , Figure 2a This diagram illustrates the variation of the sample's photoconductivity with frequency, with the vertical axis representing conductivity and the horizontal axis representing frequency variation. The real and imaginary parts of the sample's photoconductivity remain essentially unchanged with the incident angle, which is related to the high symmetry of the 2-H single-crystal structure of the few-layer molybdenum disulfide. It should be noted that if the sample is placed at an angle, an additional optical path difference, ΔL1, will occur. Where n2 is the refractive index of the substrate, θ in Where ΔL0 is the incident angle, and ΔL0 is the difference in thickness between the sample and the substrate. Please refer to [reference needed]. Figure 2b , Figure 2bThis diagram illustrates the photoconductivity of ML-MoS2 on a sapphire substrate measured using transmission and reflection terahertz time-domain spectroscopy. When using reflection terahertz time-domain spectroscopy, the phase sensitivity of the terahertz spectrum is evident: the position of the reference mirror needs to be precisely determined to prevent phase errors from influencing the calculated optical properties of the sample. Based on these conclusions, the real and imaginary parts of the photoconductivity of ML-MoS2 extracted from the transmission and reflection experimental data are essentially consistent within the range of 0.1–0.8 THz, further validating the feasibility of the extended method presented in this work. The diagram also shows the variation of the photoconductivity of ML-MoS2 with frequency at different incident angles on the sapphire substrate, along with the photoconductivity obtained from transmission and reflection terahertz time-domain spectroscopy measurements of ML-MoS2 on the sapphire substrate.

[0060] In this embodiment, the accuracy and versatility of the method are determined through experimental measurements and parameter extraction of the sample. The obtained results can be used to accurately extract the optical parameters of two-dimensional material / substrate systems, which is of great significance for accurately evaluating the physical properties of materials and various applications of terahertz time-domain spectroscopy (such as imaging and identification). This significantly promotes the overall improvement of terahertz time-domain spectroscopy measurement technology and advances the exploration of two-dimensional materials in the terahertz band. This not only greatly simplifies user operation but also improves the consistency of measurement indicators, enhancing practicality and reliability. It solves the technical problems of current terahertz time-domain spectroscopy methods for measuring spectral amplitude and phase, which are not precise enough and neglect factors such as phase difference, angle, and polarization.

[0061] Please see Figure 3 One embodiment of the two-dimensional material testing method using terahertz time-domain spectroscopy in this invention includes:

[0062] 301. The light from the generated light source enters the beam splitter to obtain the first split beam and the second split beam;

[0063] 302. The second beam of light is adjusted by the reflection of multiple metal mirrors so that the second beam of light enters the silicon wafer;

[0064] 303. The first beam of light is adjusted by the reflection of multiple metal mirrors so that the first beam of light enters the half-wave plate, ensuring that the linearly polarized light is diffracted by the LiNbO3 crystal plate to generate terahertz excitation light.

[0065] 304. By using multiple parabolic mirrors to reflect and adjust the terahertz excitation light, the terahertz excitation light is incident on the two-dimensional material on the material substrate to generate THz light containing material measurement information;

[0066] 305. Using multiple parabolic mirrors to reflect and adjust the THz light for material measurement information, so that the material measurement light enters the silicon wafer;

[0067] 306. Using a silicon wafer to receive the second beam of light and the THz light containing material measurement information to form the analytical incident light, and controlling the analytical incident light to enter the spectrometer;

[0068] 307. The spectral analyzer generates the photoconductivity of two-dimensional materials based on a preset signal acquisition algorithm.

[0069] In steps 301-307, a few layers of two-dimensional material exist at the interface (z=0) between two semi-infinite media, such as... Figure 4 As shown, Figure 4 This is a schematic diagram illustrating the principles of transmission and reflection in an embodiment of the present invention. Figure 4 In part a, a few layers of two-dimensional material exist at the interface (z = 0) between two semi-infinite media. The dielectric constants of the capping layer (z > 0) and the substrate (z < 0) are εi and εj, respectively. We assume the thickness of the two-dimensional material is d, satisfying the condition d << δ << λ, where δ is the adhesion depth and λ is the wavelength of the terahertz radiation. The two-dimensional material can be considered as a current surface, i.e., J = dσE. || The boundary conditions are that the tangential component of the electric field is continuous in the surface, while the tangential component of the magnetic field is discontinuous in the presence of surface current.

[0070] By matching the boundary conditions, the Fresnel coefficients are:

[0071]

[0072]

[0073] in For the purpose of referring to functions, For the purpose of referring to functions, For Fresnel coefficients, the vector in medium i is represented by... and c is the speed of light, and k is the speed of light in the x and z components. i k x =k i sinθ in and When there is no two-dimensional material at the interface, i.e., J = dσE || =0, the Fresnel coefficient will be reduced to the conventional form; here, we assume a few-layer two-dimensional material / substrate system, with a substrate of finite thickness L and a few-layer two-dimensional material of thickness d.

[0074] exist Figure 4 Part b is a schematic diagram of the principle of multiple transmission and reflection in the sample, and the calculation formula is shown in Table 1.

[0075] Table 1. Terahertz transmission processes of transmission and reflection.

[0076]

[0077] Figure 4 Part a takes p-polarized waves as an example, and part of it is the propagation diagram of terahertz pulses. E THz (ω) is the incident terahertz electric field, E tm (ω) is the m-order transmission electric field, E rm (ω) is the m-order reflected electric field. Medium 1 and 3 are air, while medium 2 is the substrate.

[0078] in It is the transfer factor in air at a distance zL, neglecting the thickness of the few-layer two-dimensional material (λmm>>dnm). It is the transfer factor in the substrate at a distance L, where ω is the angular frequency. and It is the complex refractive index of air and substrate. For transmission-mode terahertz time-domain spectroscopy measurements, the selected substrate has high transmittance in the terahertz band, meaning it has low coefficient absorption in the terahertz band; examples include high-resistivity silicon and sapphire. During data processing, due to the thickness of the substrate, the echoes in the time-domain spectrum can be clearly distinguished. In other words, the terahertz signal drops to zero between two echoes. Therefore, in data processing, only one main emitted terahertz pulse is intercepted, and the effects of multi-stage interference are not considered. Furthermore, the thickness of two-dimensional material samples is typically on the nanometer scale, much smaller than the wavelength of terahertz radiation, thus multiple reflections in two-dimensional materials are also ignored.

[0079] The electric fields of the terahertz wave transmission substrate and the few-layer two-dimensional material / substrate are shown below:

[0080]

[0081]

[0082] Theoretically, the complex transmission coefficient of a sample is obtained by dividing the sample signal by the substrate signal:

[0083]

[0084] The specific determination can be made according to the equation in Table 2.

[0085] Table 2. Complex Transmission and Reflection Functions

[0086]

[0087] In Table 2, when θ in =0, the temperature with respect to p- / s-polarization will decrease to be consistent with the Tinkham relation. For reflective terahertz time-domain spectroscopy, the reflectance reference signal and sample signal are as follows:

[0088]

[0089]

[0090] Theoretically, the complex reflection function can be written as:

[0091] When using reflective rather than transmissive terahertz time-domain spectroscopy, the phase sensitivity of terahertz time-domain spectroscopy is evident: precise positioning of the reference mirror is required to prevent phase errors from influencing the calculated optical properties of the sample. When positional errors are unavoidable, phase difference correction is necessary. This is a phase difference calibration function. For reflective terahertz time-domain spectroscopy, when the selected substrate has a low absorption coefficient, such as the commonly used sapphire with an absorption coefficient of ~0.001 in the terahertz band, a gold or silver mirror can be selected as a reference, and its reflectance coefficient is selected as r. metal = -1, independent of frequency.

[0092] Substituting the measurement data into the signal analysis formula yields the photoconductivity of the two-dimensional material, wherein the signal analysis formula includes:

[0093] Substituting the reflection measurement data into the signal analysis formula yields the photoconductivity of the two-dimensional material, wherein the signal analysis formula includes:

[0094]

[0095]

[0096]

[0097]

[0098] When using a flat dielectric or metal surface as a reference Among them, E THz (ω) is the electric field of the incident terahertz wave. It is a reflected reference electric field. The electric field measured on the sample, ω is the angular frequency. Here, ΔΦ is the air transfer factor, ΔΦ is the measurement phase difference, and r(ω) is the measurement amplitude ratio. To measure the value of the complex reflection function, The substrate reflectance is... Let θ be the sample reflectance coefficient. in Let n be the incident angle, n1 be the air refractive index, n2 be the substrate refractive index, and Z0 be the free-space impedance. The p-polarized complex optical conductivity of the sample. The polarization complex optical conductivity of the sample is S.

[0099] Substituting the transmission measurement data into the signal analysis formula yields the photoconductivity of the two-dimensional material, wherein the signal analysis formula includes:

[0100]

[0101]

[0102]

[0103]

[0104] It is the transmission reference electric field. The electric field measured is the sample electric field, ΔΨ is the measured phase difference, and t(ω) is the measured amplitude ratio. To measure the value of the complex reflection function, The substrate transmittance is , The sample transmittance coefficient is denoted as . The signal analysis formula further includes:

[0105]

[0106] in, The photoconductivity of the sample is [value missing]. The p-polarized complex optical conductivity of the sample. The polarization complex optical conductivity of the sample is S.

[0107] The above describes the physical principle of two-dimensional material testing methods using terahertz time-domain spectroscopy. Figure 1 The two-dimensional material testing device based on terahertz time-domain spectroscopy realizes the optical path testing of the two-dimensional material testing method based on terahertz time-domain spectroscopy.

[0108] In one embodiment, a laser pulse with a wavelength of 800 nm, a photon energy of 1.5 eV, and a pulse width of 30 fs is generated and injected into a beam splitter. Nitrogen gas is continuously supplied to the two-dimensional material testing apparatus for terahertz time-domain spectroscopy, and the humidity is maintained between 0% and 4%.

[0109] In this embodiment, the accuracy and versatility of the method are determined through experimental measurements and parameter extraction of the sample. The obtained results can be used to accurately extract the optical parameters of two-dimensional material / substrate systems, which is of great significance for accurately evaluating the physical properties of materials and various applications of terahertz time-domain spectroscopy (such as imaging and identification). This significantly promotes the overall improvement of terahertz time-domain spectroscopy measurement technology and advances the exploration of two-dimensional materials in the terahertz band. This not only greatly simplifies user operation but also improves the consistency of measurement indicators, enhancing practicality and reliability. It solves the technical problems of current terahertz time-domain spectroscopy methods for measuring spectral amplitude and phase, which are not precise enough and neglect factors such as phase difference, angle, and polarization.

[0110] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for extracting two-dimensional material parameters using terahertz time-domain spectroscopy, characterized in that, The method for extracting two-dimensional material parameters from the terahertz time-domain spectrum includes: The light from the generated light source enters the beam splitter to obtain the first and second beam splits; The second beam of light is adjusted by using the reflection of multiple metal mirrors so that the second beam of light enters the silicon wafer; The reflection of the first beam of light is adjusted by using multiple metal mirrors so that the first beam of light enters the half-wave plate, ensuring that the linearly polarized light is diffracted by the LiNbO3 crystal plate to generate terahertz excitation light. By using multiple parabolic mirrors to reflect and adjust the terahertz excitation light, the terahertz excitation light is incident on the two-dimensional material on the material substrate to generate THz light containing material measurement information; Multiple parabolic mirrors are used to reflect and adjust the THz light for material measurement information, so that the material measurement light enters the silicon wafer; The silicon wafer is used to receive the second beam of light and the THz light containing material measurement information to form the analytical incident light, and the analytical incident light is controlled to enter the spectrometer. The spectral analyzer generates the photoconductivity of two-dimensional materials based on a preset signal acquisition algorithm. The spectral analyzer, based on a preset signal acquisition algorithm, generates the photoconductivity of the two-dimensional material, including: Substituting the reflection measurement data into the signal analysis formula yields the photoconductivity of the two-dimensional material, wherein the signal analysis formula includes: Substituting the transmission measurement data into the signal analysis formula yields the photoconductivity of the two-dimensional material, wherein the signal analysis formula includes: When using a flat dielectric or metal surface as a reference It is the transmission reference electric field. The electric field measured is the sample electric field, ΔΨ is the measured phase difference, and t(ω) is the measured amplitude ratio. To measure the value of the complex reflection function, The substrate transmittance is , Let E be the sample transmittance coefficient, where E is the transmittance coefficient. THz (ω) is the electric field of the incident terahertz wave. It is a reflected reference electric field. The electric field measured on the sample, ω is the angular frequency. Here, ΔΦ is the air transfer factor, ΔΦ is the measurement phase difference, and r(ω) is the measurement amplitude ratio. To measure the value of the complex reflection function, The substrate reflectance is... Let θ be the sample reflectance coefficient. in Let n be the incident angle, n1 be the air refractive index, n2 be the substrate refractive index, and Z0 be the free-space impedance. The p-polarized complex optical conductivity of the sample. The polarization complex optical conductivity of the sample is S.

2. The method for extracting two-dimensional material parameters using terahertz time-domain spectroscopy according to claim 1, characterized in that, The signal analysis formula also includes: in, The photoconductivity of the sample is [value missing]. The p-polarized complex optical conductivity of the sample. The polarization complex optical conductivity of the sample is S.

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